Retardation films are used in various liquid crystal displays. A liquid crystal display incorporating a retardation film can have improved display characteristics because the retardation film serves to compensate a viewing angle and the birefringence of a liquid crystal cell, for example. As the retardation film, a film exhibiting an optically positive or negative uniaxiality has been used conventionally (see Patent Documents 1 and 2, for example). However, depending on the types of liquid crystal display, such a uniaxial film may not sufficiently improve the display characteristics of the liquid crystal display even if it is incorporated therein.
In order to solve this problem, an optically biaxial film with its refractive indices in three directions being controlled has been used as a retardation film (see Patent Documents 3 and 4, for example). In general, such a biaxial film is formed by biaxially stretching a polymer film. However, there still has been a problem in that such a biaxial film may cause display coloring when incorporated in a liquid crystal display.    Patent Document 1: JP 4(1992)-194820 A    Patent Document 2: JP 8(1996)-511812 A    Patent Document 3: JP 3(1991)-33719 A    Patent Document 4: JP 3(1991)-24502 A